The invention relates to a pump-inflow-cannula and a pump-outflow-cannula providing a blood conduit from a heart and/or from an associated vessel, as well as to a blood managing system comprising a pump-inflow-cannula and/or a pump-outflow-cannula, a method for connecting a pump-inflow-cannula, a method for connecting a pump-outflow-cannula, a method for connecting a blood managing system and a method for performing a bypass.
Cardiac support systems, in particular long-term cardiac support systems, are utilized as a “bridge to decision” and a “bridge to transplant” for patients requiring physiologic cardiac stability. Such cardiac support systems are typically accomplished with an extracorporeal circuit containing a blood pump and sometimes an oxygenator which are attached to the blood circulation of a patient by a pump-inflow-cannula providing a blood conduit from the heart or from an associated vessel, e.g. from a vein to the blood pump, and a pump-outflow-cannula providing a blood conduit from the blood pump back to the heart or an associated vessel, e.g. to an arteria, in particular to the aorta. That is, the cardiac connection between the patient and the extracorporeal circuit is accomplished with the pump-inflow- and pump-outflow-cannulae that are placed within the cardiac chambers or major supply vessels.
Open heart surgery cannulae typically result in utilization of less than six hours, while “bridge” cannulae or “long-term” cannulae may be used up to six months. Cannulae utilized for extended periods of time must impose minimal trauma on the blood.
For long-term cardiac support up to six months or longer, the “UltraMag Blood Pump” from Levitronix LLC has turned out to work extremely reliably and to produce minimal blood trauma. The same is true for Levitronix's “CentriMag Blood Pump”, which is intended for short-term support, typically for less than 30-day use.
The most common techniques used in Cardiac Surgery Centers for postcardiotomy support include Extracorporeal Membrane Oxygenation (ECMO) and Ventricular Assist Devices (VAD). Poor ventricular function may be diagnosed preoperatively or may have resulted from myocardial insult during surgery, for example from inadequate perfusion, cross-clamping for extended periods of time limiting reperfusion, injury, etc.
A reduced cardiac output over the years will affect other organs due to low blood pressure and blood flow. Over time, allowing the myocardium to rest may allow recovery. Thus, the patient may require long-term cardiac support. Patients who cannot be weaned from cardiopulmonary bypass and possess isolated ventricular dysfunction are probably candidates for a Ventricular Assist Device (VAD). Also well known are BiVAD support systems requiring two-pump circuits. When pulmonary dysfunction occurs, the patient is most likely a candidate for Extracorporeal Membrane Oxygenation (ECMO).
Cardiac cannulae provide the patient interface means to an extracorporeal blood circuit. A placement of these cannulae may access the vasculature through major vessels, e.g. through Right Atrium (RA), Left Atrium (LA), Left Ventricular Apex (LVA), Femoral Artery (FA), Femoral Vein (FV), Superior Vena Cava (SVC), Inferior Vena Cava (IVC) or the Aorta. Two cannulae are required in the extracorporeal circuit: one for pump inflow, the pump-inflow-cannula, and one for pump outflow, the pump-outflow-cannula.
The pump-inflow-cannula, sometimes referred to as the “venous cannula”, is the primary conduit that transitions the blood from the patient to the extracorporeal circuit. The exact placement location is at the discretion of the surgeon. Ideally, the pump-inflow-cannula may be positioned within the ventricle transitioning the heart wall with the lumen of the cannula extending just past the wall. The cannula should be stabilized by a suture purse-string or a sewing-ring to provide a means for securing the cannula against inadvertent dislodgement and to provide a leak-free connection.
The pump-outflow-cannula, sometimes referred to as the “return cannula”, or the “arterial cannula” (which may be a misnomer), is the primary conduit that transitions the blood from the extracorporeal circuit to the patient. The aorta is the preferred site for the pump-outflow-cannula but other sites may be selected at the discretion of the physician. The pump-outflow-cannula may be secured through the aortic arch and may be accomplished in a variety of ways. One way is to secure a vascular graft to the transverse arch and pass the pump-outflow-cannula through the graft lumen, but preferably not enter into the vessel, and to secure the graft to the cannula by wrapping a suture about the graft. Another possibility may be to place the tip of the cannula through the wall of the aorta and stabilize it with a purse-string suture or a tip-stabilizing device. The pulmonary artery is also a common point of blood return.
The distal-end of the pump-inflow-cannula, that is, the end which is connected to the extracorporeal circuit, is passed through a dilated tunnel created from the ventricle through the subcutaneous plane to the percutaneous access site. The pump-outflow-cannula is passed through a dilated tunnel created from the arch of the ascending aorta through the subcutaneous plane to the percutaneous exit site. The percutaneous access sites are located ipsilaterally, on the left abdominal wall for the Left Ventricular Assist Device (LVAD), in the medial anterior position. The location is ipsilateral on the right abdominal wall for a Right Ventricular Assist Device (RVAD), in the medial anterior position. The extracorporeal system is attached to the pump-inflow- and the pump-outflow-cannulae using good perfusion technique. The open chest wound is closed upon successfully administrating the support system.
The support system, in particular the pump-inflow- and pump-outflow-cannulae known from the state of the art, has several disadvantages, in particular with respect to the blood transfer from the heart and/or from the associated vessels into the pump-inflow-cannula as well as with respect to the transfer of the blood out of the pump-outflow-cannula into the heart or into the associated vessel. Over extended periods of time, very low flow rates can initiate blood clots that can release and become lodged down-stream in the pump, oxygenator or patient organs. Furthermore, the attachment of the known cannulae to the patient is difficult to handle and, what is more, the known cannulae can be easily compressed and/or bent, which can easily lead to a cross-clamping of the cannula, resulting in an interruption of the blood flow through the extracorporeal support system, which may cause serious consequences for the patient's physical health and, at worst, may lead to a life-threatening situation for the patient.